Method of controlling shelf life of packaged produce

ABSTRACT

To control shelf life of package produce, a first produce is placed inside an inner gas-permeable package. The inner gas-permeable package is sealed, thereby creating a first package atmosphere inside the inner package. A second produce is placed inside an outer gas-permeable package. The sealed inner package is contained within the outer gas-permeable package. The outer gas-permeable package is also sealed, thereby creating a second package atmosphere inside the outer bag. The first package atmosphere controls the shelf life of the first produce, and the second package atmosphere controls the shelf life of the second produce. The produce inside each inner and outer bag may include one or more vegetables, fruits, and nuts.

BACKGROUND

1. Field

The present disclosure relates generally to packaging of fresh produce, and more specifically to packaging of fresh vegetables and fruits in gas-permeable bags.

2. Description of Related Art

The freshness of packaged produce is affected by the packaging used to modify or control the atmosphere surrounding the produce. Controlling the shelf life of fresh produce, such as fresh vegetables and fruits, is desirable for wholesalers, retailers, and end-consumers. In particular, controlled shelf life leads to less spoiled produce. Wholesalers can avoid delivery of spoiled goods to retailers, and thus, more efficiently use transportation resources. Retailers can better control inventory, and also offer end-consumers a product that visually looks more appealing. End-consumers can keep the packaged produce for a longer period of time without significantly compromising the freshness and taste of the produce.

In the conventional fresh produce packaging industry, shelf life can be controlled by modified-atmosphere packaging and controlled-atmosphere packaging. In modified-atmosphere packaging, air is removed from the packaging and replaced with a gas or a mixture of gases. Once the package is sealed, the atmosphere inside the package may change due to respiration of the packaged product, and permeation of gases through the packaging material. In controlled-atmosphere packaging, gases are introduced into the package through the storage period to actively maintain the package atmosphere.

The gas mixture inside the package atmosphere may depend on the product. Different types of produce may consume oxygen (O₂) and release carbon dioxide (CO₂) at different rates, depending on their stage of development and the surrounding atmosphere and temperature. As such, controlling the atmosphere inside a package with two or more produce types may be challenging, since each produce has a different effect on the package atmosphere. Thus, what is needed in the art is a method of controlling shelf life for a package containing two or more produce that may affect the package atmosphere differently, and coordinating the gas release of the produce to achieve optimal package atmospheres for each produce.

BRIEF SUMMARY

In one exemplary embodiment to control shelf life of packaged produce, a first produce is placed inside an inner gas-permeable package, which is then sealed. A second produce is placed inside an outer gas-permeable package, along with the sealed inner gas-permeable package. The outer gas-permeable package is then sealed. The inner gas-permeable package has a first gas permeability rate, and the outer gas-permeable package has a second gas permeability rate. The first and second gas permeability rates are different to control shelf life of the first and second produce. The gas permeability rates may, for example, be oxygen transfer rates.

DESCRIPTION OF THE FIGURES

The present application can be best understood by reference to the following description taken in conjunction with the accompany drawing figures, in which like parts may be referred to by like numerals:

FIG. 1 depicts an exemplary produce package, with perforated inner and outer bags;

FIG. 2 depicts an exemplary inner bag containing shredded carrots, shredded red cabbage, and shredded radishes;

FIG. 3 depicts an exemplary inner bag containing grape tomatoes; and

FIG. 4 depicts an exemplary inner bag containing snap peas.

DETAILED DESCRIPTION

The following description sets forth numerous specific configurations, parameters, and the like. It should be recognized, however, that such description is not intended as a limitation on the scope of the present disclosure but is instead provided as a description of exemplary embodiments.

The following description relates primarily to the commercial packaging of fresh produce. Currently, single types of vegetables and fruits are packaged into a sealed bag or container. For example, consumers may find a bag of baby carrots, a bag of celery sticks, a container of sliced watermelon or pineapple, or a bag of chopped lettuce in a retail store. In order to control the freshness of the packaged vegetable or fruit, certain materials that can control gas permeability are typically used for packaging.

As discussed above, fresh vegetables and fruits respire by consuming oxygen (O₂) and releasing carbon dioxide (CO₂). Different types of vegetables and fruits will release and consume oxygen and carbon dioxide, respectively, at different rates. The presence of one type of fruit or vegetable can change the atmosphere needed to control, maintain or extend shelf life for another type of fruit or vegetable. As such, one packaging atmosphere for multiple produce types in a single bag or container may not be sufficient to maintain the freshness for each produce type inside the bag or container.

FIG. 1 depicts an exemplary produce package 100 that may contain at least two produce types. Package 100 includes two bags: outer bag 102 and inner bag 104. Each bag in package 100 has an atmosphere within the bag that is suitable for controlling, maintaining or extending shelf life of the produce inside that bag.

Inner bag 104 typically fits inside outer bag 104. It should be understood, however, that package 100 may include more than one inner bag. Package 100 may include one, two, three, four or five inner bags. In some embodiments, multiple inner bags may be placed inside outer bag 104. In other embodiments, one or more inner bags may be placed inside another inner bag.

FIGS. 2-4 are exemplary embodiments of inner bags that can be placed inside an outer bag. With reference to FIG. 2, inner bag 202 contains mixed vegetables 204, which include shredded carrots, shredded red cabbage, and shredded radishes. With reference to FIG. 3, inner bag 302 contains grape tomatoes 304. With reference to FIG. 4, inner bag 402 contains snap peas 404. Inner bags 202, 302 and 402 may be placed individually or in combination inside an outer bag containing, for example, spring mix or lettuce.

With reference again to FIG. 1, both outer bag 102 and inner bag 104 are each independently sealed. Outer bag 102 and inner bag 104 can be independently sealed by any means known in the art. In one exemplary embodiment, outer bag 102 and inner bag 104 may both be heat sealed. In other embodiments, outer bag 102 and inner bag 104 may each independently be sealed using any adhesive known in the art, or using a fastener, such as by a wire, cord, rubber band, and the like.

Each sealed bag has a package atmosphere. Once sealed, outer bag 102 has package atmosphere 110, and inner bag 104 has package atmosphere 112. It should be understood that package atmosphere 110 refers to the atmosphere outside inner bag 104 but inside outer bag 102. The term “package atmosphere” as used herein refers to the concentration of gases (e.g., oxygen, carbon dioxide, ethylene) inside a bag or container.

In some embodiments, package atmosphere 110 may be higher, lower, or the same as package atmosphere 112. The desired atmosphere inside each bag will depend on the type of produce (e.g., vegetable, fruit) present inside the bag, and the optimal gas concentration needed by that type of produce to control, maintain or extend shelf life. For example, with reference to FIG. 2, inner bag 202 containing mixed vegetables 204 has an oxygen transfer rate of about 200-300 cc O₂/100 in²/day. This oxygen transfer rate helps maintain the freshness of mixed vegetables 204, by controlling the oxygen level inside the bag at around 20%.

Outer bag 102 and inner bag 104 can independently be constructed of any material known in the art that may be permeable to gases, such as oxygen, carbon dioxide, nitrogen, and ethylene. In one exemplary embodiment, outer bag 102 and inner bag 104 is formed from a plastic material. The plastic material can be made of any single resin or combination of a plurality of resins. Exemplary resins include, but are not limited to, low density polyethylene, linear low density polyethylene, high density polyethylene, polypropylene, butadiene, polystyrene, polyester, or any combination of these material. In another exemplary embodiment, outer bag 102 and inner bag 104 can independently be made of polymers, or have added materials that modify the permeability of outer bag 102 and inner bag 104 to oxygen and carbon dioxide. Outer bag 102 and inner bag 104 may be made of the same or different materials.

It should be recognized that different portions of outer bag 102 and inner bag 104 can be formed to have permeability to oxygen and/or carbon dioxide. For example outer bag 102 and inner bag 104 can independently be formed with some portions permeable to oxygen and other portions permeable to carbon dioxide. The percent of the portions permeable to oxygen compared to the percent of the portions permeable to carbon dioxide can determine the overall permeability characteristic of outer bag 102 and inner bag 104.

In one exemplary embodiment, outer bag 102 and inner bag 104 can independently have one or more perforations. Perforations can be of any size and shape. For example, perforations having a diameter between about 20 microns to about 12.5 mm can be used. The perforations can be visible to the naked eye or only under microscopic viewing. In some embodiments, outer bag 102 may be perforated, whereas inner bag 104 is not perforated. In other embodiments, neither or both outer bag 102 and inner bag 104 may be perforated. If both outer bag 102 and inner bag 104 are perforated, each bag may have different size perforations.

The walls of outer bag 102 and inner bag 104 can independently have any thickness. In one exemplary embodiment, the walls of outer bag 102 and inner bag 104 independently have a thickness anywhere from about 0.00025 to 0.05 inches. In other exemplary embodiments, the thickness of the walls of outer bag 102 and inner bag 104 can independently be equal to or greater than about 0.00025, 0.0005, 0.00075, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.025, 0.03, 0.04, or 0.05 inches. In further exemplary embodiments, the thickness of the walls of outer bag 102 and inner bag 104 can independently be equal to or less than about 0.05, 0.04, 0.03, 0.025, 0.02, 0.01, 0.009, 0.008, 0.007, 0.006, 0.005, 0.004, 0.003, 0.002, 0.001, 0.00075, 0.0005, or 0.00025 inches.

The material used for each bag, the size and number of perforations, and the thickness of the bag may also affect the gas permeability of outer bag 102 and inner bag 104, which in turn affects the package atmosphere of outer bag 102 and inner bag 104. As used herein, the term “gas permeability” refers to the transport of gasses, such as oxygen and carbon dioxide, across a membrane. Unless as otherwise indicated, gas permeability refers to all gases in general. As used herein, “oxygen transfer rate” (also known as “OTR” or “oxygen transmission rate”) refers to the oxygen (O₂) permeability. OTR may be measured by any method known in the art, including, for example, ASTM International standard test methods (e.g., D3985, F1307, F1927, or F2622) or ambient oxygen ingress rate method (AOIR). In some embodiments, outer bag 102 and inner bag 104 independently have an OTR of at least 100 cc O₂ /100 in²/day. The OTR of the bags can be chosen to optimize or extend shelf life of the produce inside the bag. In other embodiments, outer bag 102 and inner bag 104 independently have an OTR between 100-1000 cc O₂/100 in²/day, 100-500 cc O₂/100 in²/day, 200-400 cc O₂/100 in²/day or 275-350 cc O₂/100 in²/day.

It should also be recognized that various types of containers can be used in addition to outer bag 102 and inner bag 104. The container may be hard or soft. Outer bag 102 and inner bag 104 may be different types of containers.

Outer bag 102 and inner bag 104 independently contain one or more produce. Produce may include vegetables (e.g., lettuce, spinach, cabbage, carrots), fruits (e.g., tomatoes, strawberries, apples), or nuts (e.g., walnuts, almonds, pine nuts). In some embodiments, outer bag 102 and inner bag 104 may independently contain one, two, three, four, or five produce. The one or more produce inside outer bag 102 and inner bag 104 may be the same or different.

EXAMPLES

The following examples demonstrate how different vegetables and fruits may be packaged in two or more gas-permeable bags to control shelf life of the produce using differential package atmospheres.

Example 1 Spinach and Spring Mix with Tomato

3.25 oz of grape tomatoes were placed in a 6 inch by 4 inch bag. This inner bag made of polyethylene had 24 perforations total, 3 perforations across the width of the bag and 4 perforations down the height of the bag. Each perforation was about 30 microns in diameter. This inner bag was sealed, with 20.0% oxygen.

4.5 oz of spinach and spring mix, which included baby lettuce and baby greens, were placed in an 18.875 inch by 12.5 inch bag. This outer bag made of polyethylene/polypropylene had about 160-165 perforations total, with 0.3 inches between perforations and two rows of perforations on each side of the bag. Each perforation was about 105 microns in diameter. The sealed inner bag was placed inside the outer bag, and then the outer bag was sealed, with 20.95% oxygen.

The package atmosphere of the inner and outer bags was tested to determine the oxygen and carbon dioxide concentration on Day 0, Day 7 and Day 14. The data is summarized in Table 1 below.

TABLE 1 O₂ and CO₂ concentrations in packaged spinach and spring mix with tomato Inner Bag (Tomatoes) Outer Bag (Spinach, Spring Mix) Day O₂ CO₂ O₂ CO₂ 0 20.0% 0.0% 20.0% 0.0% 7 18.7% 2.6% 18.0% 3.2% 14 20.4% 1.2% 20.7% 3.5%

Based on the data presented in Table 1, it was observed that the amount of oxygen in the package atmosphere was maintained at around the optimal level of 20% to maintain freshness of the spinach and spring mix in the outer bag and the tomatoes in the inner bag. It was also observed that the carbon dioxide concentration inside each package increased slightly as each produce released carbon dioxide over time; however, the increase in the amount of carbon dioxide was controlled to minimize anaerobic reactions that can affect product quality.

Example 2 Spring Mix with Mixed Vegetables

1.33 oz of each shredded carrots, shredded red cabbage, and shredded radishes (total 4 oz), were placed in an 8 inch by 5 inch bag. This inner bag was made of polyethylene, and had an oxygen transfer rate of 300 cc O₂/100 in²/day. This inner bag was sealed, with 20.0% oxygen.

4 oz of spring mix, which included baby lettuce and baby greens, were placed in an 18.875 inch by 12.5 inch bag. This outer bag made of polyethylene/polypropylene had about 160-165 perforations total, with 0.3 inches between perforations and two rows of perforations on each side of the bag. Each perforation was about 105 microns in diameter. The sealed inner bag was placed inside the outer bag, and then the outer bag was sealed, with 20.0% oxygen.

The package atmosphere of the inner and outer bags was tested to determine the oxygen and carbon dioxide concentration on Day 0, Day 7 and Day 14. The data is summarized in Table 2 below.

TABLE 2 O₂ and CO₂ concentrations in packaged spring mix with mixed vegetables Inner Bag (Mixed Vegetables) Outer Bag (Spring Mix) Day O₂ CO₂ O₂ CO₂ 0 20.0% 0.0% 20.0% 0.0% 7 0.6% 8.5% 17.3% 3.9% 14 0.5% 7.4% 17.1% 3.8%

Based on the data presented in Table 2, it was observed that the mixed vegetables (i.e., shredded carrots, shredded red cabbage, and shredded radishes) consumed a portion of the oxygen inside the inner bag, and released carbon dioxide into the package atmosphere of the inner bag. Due to the permeability of the inner bag, a portion of the oxygen may have also been transferred into the package atmosphere of the outer bag. Oxygen content inside the outer bag remained high, thereby maintaining the freshness of the spring mix.

Example 3 Sweet Baby Lettuce with Carrots and Red Cabbage and Snap Peas

2.5 oz of sugar snap peas were placed in a 6 inch by 4 inch bag. This inner bag made of polyethylene had 24 perforations total, 3 perforations across the width of the bag and 4 perforations down the height of the bag. Each perforation was about 30 microns in diameter. This inner bag was sealed, with 20.0% oxygen.

6.25 oz of sweet baby lettuce was placed in an 18.875 inch by 12.5 inch bag. This outer bag made of polyethylene/polyproplyene had about 160-165 perforations total, with 0.3 inches between perforations and two rows of perforations on each side of the bag. Each perforation was about 105 microns in diameter. The sealed inner bag was placed inside the outer bag, and then the outer bag was sealed, with 20.0% oxygen.

The package atmosphere of the inner and outer bags was tested to determine the oxygen and carbon dioxide concentration on Day 0, Day 7 and Day 14. The data is summarized in Table 3 below.

TABLE 3 O₂ and CO₂ concentrations in packaged sweet baby lettuce with carrots and red cabbage and snap peas Outer Bag (Baby lettuce, Inner Bag (Snap Peas) Carrots, Red Cabbage) Day O₂ CO₂ O₂ CO₂ 0 20.0% 0.0% 20.0% 0.0% 7 0.4% 11.0% 20.5% 0.4% 14 0.3% 10.0% 20.5% 0.6%

Based on the data presented in Table 3, it was observed that the snap peas consumed a portion of the oxygen inside the inner bag, and released carbon dioxide into the package atmosphere of the inner bag. Due to the permeability of the inner bag, a portion of the oxygen may have also been transferred into the package atmosphere of the outer bag. Oxygen content inside the outer bag remained high, thereby maintaining the freshness of the baby lettuce, carrots and red cabbage. 

What is claimed is:
 1. A method of controlling shelf life of packaged produce by differential gas permeability, the method comprising: placing a first produce inside an inner gas-permeable package, wherein the inner gas-permeable package has a first gas permeability rate; sealing the inner gas-permeable package; placing a second produce inside an outer gas-permeable package, wherein the outer gas-permeable package has a second gas permeability rate; and sealing the outer gas-permeable package, wherein the outer gas-permeable package surrounds the inner gas-permeable package, and wherein the first gas permeability rate is different than the second gas permeability rate to control shelf life of the first produce and the second produce.
 2. The method of claim 1, wherein the first gas permeability rate and the second gas permeability rate are each an oxygen transfer rate.
 3. The method of claim 2, wherein the first gas permeability rate and the second gas permeability rate are independently an oxygen transfer rate of at least 100 cc O₂/100 in²/day.
 4. The method of claim 1, wherein the sealed inner package has a first package atmosphere, wherein the first package atmosphere controls the shelf life of the first produce, wherein the sealed outer package has a second package atmosphere, and wherein the second package atmosphere controls the shelf life of the second produce.
 5. The method of claim 4, wherein the first package atmosphere is the same, higher or lower than the second package atmosphere.
 6. The method of claim 1, wherein the inner gas-permeable package has one or more perforations.
 7. The method of claim 6, wherein each perforation of the inner gas-permeable package has a diameter greater than or equal to about 20 microns and less than or equal to about 12.5 nm.
 8. The method of claim 1, wherein the outer gas-permeable package has one or more perforations.
 9. The method of claim 8, wherein each said perforation of the outer gas-permeable package has a diameter greater than or equal to about 20 microns and less than or equal to about 12.5 nm.
 10. The method of claim 1, wherein the inner gas-permeable package and the outer gas-permeable package each independently comprises a material selected from the group consisting of low density polyethylene, linear low density polyethylene, high density polyethylene, polypropylene, butadiene, polystyrene, polyester, or any combination thereof.
 11. The method of claim 1, wherein the first produce is the same or different as the second produce.
 12. The method of claim 1, wherein the first produce and the second produce are each independently one or more vegetables, fruits, or a combination thereof. 